It's bleeding in my belly button only when i bend or sit for a while. there is no pain and only small amount of smelly blood appears.

This could be: Related to your blood clotting abnormality. Follow up with your dr for a thorough exam. Or perhaps it could just from a minor irritation. Best wishes!

Naval bleeding: Belly button bleeding can have a few causes. Sometimes dirt can embed itself and cause an infection, which can cause the smelly blood you describe. Some people can have a problem called a urachal cyst which is caused by an error during fetal development, so that a small opening in the naval leads to a pocket behind it. This can get infected. See your doctor for an exam and diagnosis.